<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script>
      var num = 1;
      console.log(typeof num); //number
      var str = "1233";
      console.log(typeof str); //string
      var flag = true;
      console.log(typeof flag); //boolean
      var vari1 = undefined;
      console.log(typeof vari1); //
      var timer = null;
      console.log(typeof timer);
      //prompt取过来的值是字符型
      var age = prompt("请输入年龄");
      console.log(age);
      console.log(typeof age);
    </script>
  </head>
  <body></body>
</html>
